EFFECTS OF SONICATION OF CLINICAL SPECIMENS ON DETECTION OF CYTOMEGALOVIRUS IN SHELL VIAL CULTURES

Background: The centrifugation-enhanced shell vial (SV) method of viru s culturing has decreased the time to laboratory detection of many vir uses, and has become the principal method for the rapid detection of c ytomegalovirus (CMV) in clinical specimens. Objectives: To examine the use of sonication and centrifugation of clinical specimens as a means of optimizing the sensitivity of SV detection of CMV, decreasing the toxicity of specimens to the SV monolayer, and facilitating the examin ation and interpretation of SV monolayers. Study design: A total of 35 0 clinical specimens submitted for CMV culture were processed and then divided in half with one-half sonicated for 1 min in a cup-horn-equip ped sonicator, and the other half left unsonicated. Sonicated specimen s were centrifuged to recover a cell-free supernatant. SVs containing MRC-5 fibroblast monolayers were inoculated with either the unsonicate d whole specimen or the cell-free supernatant, and were stained with m onoclonal antibodies directed against the immediate-early antigen of C MV after 24 and 48 h of incubation. Results: While no significant diff erence was observed in the overall number of specimens in which CMV wa s detected following sonication, sonication did afford a 31% increase in the number of CMV-positive specimens detected at 24 h. A significan t reduction in toxicity of all specimens except for blood was observed for the sonicated specimens, although sonication of blood increased t he number of blood specimens toxic to the monolayer by 40%. Use of the cell-free inoculum following sonication facilitated microscopic exami nation and interpretation of SV monolayers without adversely affecting the sensitivity of the culture. Conclusions: Sonication of clinical s pecimens prior to shell vial culturing for CMV is beneficial and can h elp to reduce specimen toxicity, facilitate interpretation of monolaye rs, and allow the earlier detection of a positive specimen.